The present invention relates to the field of sources of high energy photons and more particularly, to the field of sources of gamma rays.
Routine energy and efficiency calibration of high-resolution HPGe (high purity Ge) detectors and other gamma ray detectors is limited to gamma ray energies of less than 2.6 MeV using normally available radioactive materials as the source of the gamma rays. Secondary radioactive standards that can be produced with a cyclotron extend the range to 3.5 MeV (56Co, t1/2=77 days) or 4.8 MeV (66Ga, t1/2=9.5 hr). These higher energy calibration standards are not readily accessible to most users and all radioactive sources require continuous safe storage since they are controlled radioactive materials.